This application claims the priority of German patent 198 28 308.3, filed Jun. 25, 1998, the disclosure of which is expressly incorporated by reference herein.
This application is related to U.S. patent application Ser. No. 09/344,247, which is a counterpart of German patent application 198 28 307.5.
The invention relates to a cylinder head of an internal-combustion engine with a device for returning lubricating oil from the interior of the cylinder head.
From German Patent Document DE 27 37 901 A1, a cylinder head of this type is known, in which an overhead camshaft is disposed. The interior receiving the camshaft is divided in the longitudinal direction of the cylinder head by transverse walls into individual subspaces. These transverse walls simultaneously form the bearing of the camshaft. Each of these subspaces is connected by way of an opening with a collector constructed on the underside of the cylinder head housing.
Furthermore, from German Patent Document DE 40 07 939 C1, a cylinder head is known in which--without any explicit representation or description--two overhead camshafts are disposed. On the exterior side of the cylinder head, a separate collector is fastened which is connected with the interior by way of several bores arranged in the cylinder head and distributed along the longitudinal course. By way of these bores, the lubricating oil which collects in the interior of the cylinder head and flows out at the different bearing points, is guided into the collector which is connected by way of a pump and a return flow pipe with the oil storage tank of the internal-combustion engine. In the oil-carrying interior of the cylinder head, relatively large amounts of oil are carried which flow out at the bearing points of the camshafts and of the bucket tappets or valve levers. Such cylinder heads have the disadvantage that this oil can spread almost unhindered in the interior before it changes by way of the lateral ducts into the oil collector. Because of the longer dwell time of this oil in the interior, an increased foaming of the oil may occur. In this case, larger free oil quantities in the interior of the cylinder head as well as an increased foaming of the oil are critical with respect to the oil circulation of the internal-combustion engine.
It is therefore an object of the invention to improve a cylinder head of an internal-combustion engine with a device for returning lubricating oil from the interior in such a manner that the oil carried freely in the interior is foamed as little as possible and reaches the scavenging point over a short distance. Furthermore, the oil quantities situated freely in the interior of the cylinder head are to be minimized and a collection of larger oil quantities in the interior during accelerations/decelerations and/or cornering is to be avoided.
According to the invention, this and other objects have been achieved by providing a cylinder head of a multi-cylinder internal-combustion engine having two overhead camshafts, comprising: a cylinder head defining an interior space for receiving said camshafts, said cylinder head defining at least one collector which extends in a longitudinal direction of the cylinder head and which is connected with a suction connection of a pump, said interior space being divided into a plurality of subspaces by longitudinal walls located between the two camshafts and by at least one transverse wall, at least some of said subspaces being connected with a collector.
According to the invention, this and other objects have been achieved by providing a cylinder head, comprising a camshaft housing including: a pair of longitudinal exterior walls; a pair of end exterior walls extending between respective ends of said longitudinal exterior walls, said longitudinal exterior walls and said end exterior walls defining an interior space; at least one transverse wall extending between said longitudinal exterior walls through said interior space and defining first and second bearings for supporting first and second camshafts, respectively; at least one longitudinal wall extending between said end exterior walls through said interior space at a location between said first and second bearings of said at least one transverse wall, said at least one transverse wall and said at least one longitudinal wall dividing said interior space into a plurality of subspaces; and a longitudinally-extending oil collecting duct.
Due to the division of the cylinder head in the longitudinal and transverse direction, defined subspaces are formed which limit the expansion of the oil which is in each case carried freely in the subspaces. From these subspaces, the oil emerging at the bearing points can be guided along a short distance to the collector, in which case the dwell time of the oil in the interior of the cylinder head is clearly reduced. By limiting the free space and by rapidly feeding the oil to the collectors, it is ensured that the foaming of the oil remains slight.
Such a partitioning of the interior can take place in a particularly advantageous manner if the bearing sections for receiving the camshafts are constructed as transverse walls and extend continuously to the respective adjoining side walls. By the integration of the function of the camshaft bearing and the transverse wall for the partitioning of the interior, sufficient free space remains for housing the cams and the stroke transmission elements, such as the bucket tappets or valve levers.
If the partitioning of the interior aligned in the longitudinal direction of the cylinder head is constructed by two longitudinal walls, the space in-between can be used particularly advantageously as an oil-free space for receiving a spark plug or an injection system. By means of such a partitioning, not only the above-described advantages with respect to the guiding of oil are achieved but, in addition, a very stiff structure of the cylinder head is achieved.
A particularly fast oil scavenging from the cylinder head with paths which are as short as possible is permitted if the collector is arranged on the underside of the subspaces which are on the bottom in the installed position. It is also advantageous for the connections to the lower subspaces and to the upper subspaces disposed above to be arranged above one another.
A scavenging of the oil which is fast also in the case of fluctuating oil levels as the result of accelerations/decelerations and/or cornering is permitted if the subspaces are connected with the collector by way of two openings arranged on opposite walls. As a result, it is ensured that also in the event of considerably fluctuating oil levels within the subspaces, a short and fast connection to the collector is ensured at any time. If such a cylinder head is arranged, for example, in the longitudinal direction, these connections can advantageously be arranged at the respective forward and rearward end of the subspace so that the fluctuations of the oil level are taken into account mainly during an acceleration and deceleration.
Due to the arrangement of a second collector on the cylinder head, which collector is constructed separately from the first collector and of which one collector is connected in the forward or rearward area of the cylinder head with the interior, while the other collector is connected in the opposite rearward and forward area of the cylinder head with its interior, also the oil which collects in the event of high accelerations almost completely in an end area of the cylinder head can be scavenged because an oil level occurs at any time in at least one of the two collectors which--without taking in air--can be scavenged by the oil pump. Due to such a construction of the cylinder head, it is possible to reliably scavenge the oil accumulating in the interior despite fluctuations of the oil level because of accelerations or cornering without the requirement of movable components, such as valves, flap valves or similar structural components.
A particularly reliable oil scavenging is advantageously ensured when both collectors are connected with one another at their end facing away from the suction point. If, in the case of such a cylinder head, the oil situated in the cylinder head because of accelerations accumulates essentially in the area of this connection point, the oil situated in the first collector can also be scavenged by way of the connection of the two collectors.
The collectors can be constructed in a particularly advantageous manner and at reasonable cost if, in the case of cast components of the cylinder head, they are also cast in so that neither external pipes, screwed connections with corresponding tightness problems nor long bores with corresponding expenditures during the manufacturing are required.
It is also advantageous for the two collectors to be constructed in different components of the cylinder head, in which case a particularly simple connection of the two collectors can take place by way of a common flange surface.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.